By Dial A Vet Veterinary Team
Last updated: 2 November 2026
Neosporosis is one of the more upsetting diagnoses a breeder or new puppy owner can hear. A litter that looked healthy at birth starts to struggle with its back legs a few weeks later, and the stiffness gets worse rather than better. The cause is a microscopic parasite called Neospora caninum. Adult dogs can be affected too, usually with nerve or muscle problems. Treatment works best when it starts early, before the legs become rigid, so recognising the pattern quickly can change the outcome.
Key takeaways
- Neosporosis is caused by Neospora caninum, a single-celled parasite related to Toxoplasma.
- Dogs are the main host of the parasite. They catch it from eating infected tissue, especially cattle placenta and foetal membranes, or from their mother before or after birth.
- Most signs appear in puppies under six months, sometimes from as young as three weeks. Hind legs become weak and then stiff and straight.
- Adult dogs can develop nerve or muscle disease, often when their immune system is weakened.
- Treatment can slow or stop the disease if started before the muscles contract. It does not always work, and relapses are common.
- Neospora is not considered a risk to people.
How dogs catch Neospora
Dogs are both the main host of Neospora and, at times, its victim. The parasite cycles between dogs and grazing animals, especially cattle, in which it is a leading cause of abortion.
The Companion Animal Parasite Council (CAPC) describes two main routes into dogs:
- Eating infected tissue. Cattle placenta and foetal membranes are the classic source, which is why farm and rural dogs are more often exposed. Raw meat from other infected animals can also carry the parasite.
- From mother to puppies. A bitch with a dormant infection can pass the parasite to her puppies late in pregnancy or through milk. This is how whole litters become affected.
CAPC also notes that dogs living around cattle, free-roaming dogs and rural dogs are more likely to have been exposed.
Signs in puppies
The Merck Veterinary Manual notes that signs usually appear in dogs under six months old and can start as early as three weeks of age. Typical signs include:
- Weakness in the hind legs that gradually gets worse
- Hind legs held rigidly straight, often stretched out behind the puppy
- Muscle wasting in the back legs
- Difficulty walking, then inability to stand on the back legs
- Weakness in the neck and trouble swallowing in advanced cases
More than one puppy in a litter is often affected. Without treatment, the muscles can tighten into permanent contractures, and the disease can be fatal.
Signs in adult dogs
Adult disease is less common and usually milder, but it can be serious. Merck describes it as arising either from a new infection or from a dormant infection that reactivates because of pregnancy or a condition that weakens the immune system. Signs can include:
- Wobbliness, tremors or loss of coordination
- Weakness, muscle pain, swelling or muscle wasting
- Difficulty swallowing
Less commonly, the parasite affects the skin, heart or lungs.
When to see a vet
Book a vet visit within a day if:
- A puppy is walking oddly, dragging its back legs or seems stiff
- A puppy cannot keep up with its littermates
- An adult dog develops weakness, wobbliness or painful muscles
Go to a vet urgently if a dog cannot stand, cannot swallow, or is struggling to breathe. With neosporosis, delay matters. Merck notes that treatment is most effective before contractures develop.
How vets diagnose it
Diagnosis can be challenging. Your vet will ask about the litter, the mother's history, access to cattle or raw meat, and when signs began. Blood tests can detect antibodies to Neospora, and PCR tests look for the parasite's genetic material. In some dogs a muscle biopsy is needed. Vets often test for Toxoplasma at the same time because the two infections look so similar. In fact, neosporosis was mistaken for toxoplasmosis until it was described as a separate disease in 1984.
Treatment and outlook
Treatment uses antibiotics that act against the parasite, usually for at least four weeks and sometimes longer. Your vet will choose the medicines and plan based on your dog's condition. Gentle physiotherapy, such as passive range of motion exercises and massage, may help some dogs.
CAPC recommends treating all littermates of an affected puppy, even if they look normal, because they may be infected too.
The honest picture is that treatment is often only partly effective. The medicines act on the active parasite but not on dormant cysts, and nerve damage that has already happened may not reverse. Merck notes that adult dogs do much better than young puppies. CAPC summarises a UK study of dogs with neurological neosporosis in which full recovery was rare and relapses were common, so ongoing monitoring with your vet is important.
Prevention
- Keep dogs away from calving areas, and do not let them eat placentas, foetal membranes or dead stock.
- Avoid feeding raw meat, particularly beef offal.
- Do not breed from a bitch that has had neosporosis or has produced affected puppies before.
- Prevent dogs from toileting in cattle feed and water, which protects herds from infection.
- If your dog has tested positive, tell any vet treating it in future. CAPC advises avoiding steroids and other immune-suppressing medicines in these dogs where possible, as they can reactivate the infection.
There is no vaccine for neosporosis in dogs.
FAQ
Can neosporosis spread to people?
Neospora is not considered zoonotic. No human illness has been linked to it.
Can a puppy recover from neosporosis?
Some do, especially when treatment starts before the legs become rigid. Others improve only partly, and some do not respond. Your vet can give you a realistic outlook for your puppy.
Should I worry if my dog lives on a farm?
Farm dogs are more often exposed. Keeping them away from calving paddocks and dead stock lowers the risk for your dog and for the herd.
Can neosporosis come back?
Yes. The parasite can stay dormant in muscle and nerve tissue and reactivate later, especially during pregnancy or illness.
Talk with a vet
If your puppy is moving strangely or an older dog has become weak or wobbly, Dial A Vet's real vets and vet nurses can talk it through with you on a video consult and help you work out how soon your dog needs to be examined in person. Dial A Vet consults cover dogs and cats. Related reading: toxoplasmosis in dogs and polymyositis in dogs. Book a video consult with Dial A Vet.
References
- Merck Veterinary Manual. Neosporosis in Dogs.
- Companion Animal Parasite Council. Neosporosis.
Disclaimer: Educational only. This page does not replace an examination or advice from your own veterinarian. If you are worried about your pet right now, contact your local vet or nearest emergency animal hospital.